@neauoire Back in school I made my own, which probably wasn't my smartest move. Two pieces of glass from welding goggles, a red gel filter and a blue gel filter, glued on sunglassed "borrowed" from my sister. Tested it with various strong lamps. Also only did one side, the other was covered up just in case and used it more no more than like 10 seconds at a time. Still not exactly a good idea.

I have gotten a lot more careful since then...